What should I weigh? The answer might be based
on your age (older women will need to weigh less)
, on your desire to be at low risk for death due to
obesity-related diseases, or just according to how
you wish your body to look. As far as your health
goes, avoiding an excessive amount of body fat is
the best way to lower your risk from heart disease,
hypertension, diabetes and even from developing gall
bladder disease. Sometimes, it is questionable as
to what is ideal body weight. A recent journal supplement,
Chez RA (ed.): Weighing the options on managing obesity.
Contemporary Ob/Gyn 1999; June supplement:3-30, looks
at the issues of weight and health and what is the
best way to manage weight problems.
Is the body mass index (BMI) the best measure of
how much fat is in my body?
Body mass index, BMI, is only an indirect measurement
of body fat. For scientific research purposes there
are more accurate methods of measuring what percent
of a body's weight is composed of fat such as hydrodensitometry
(underwater weighing) and dual-energy x-ray absorptiometry.
Physical measurements such as waist and hip circumferences
and skin fold thickness in the back of the elbow are
also used.
The BMI happens to be the most commonly used measurement
in epidemiologic studies and for middle-aged men and
women, it correlates over 90% with fat mass densitometry.
For older adults who tend to have less muscle mass
proportionally, it loses some of its accuracy as an
absolute measurement. The BMI is also called the Quetelet
index and is calculated by the weight in kilograms
divided by the square of the height in meters. While
it does not distinguish fat mass from lean or muscle
mass, it is a very useful approximation to what one
should weigh depending on height.
What are the health complications of obesity?
In order to determine what people should weigh, researchers
have looked at risk of death by different BMI categories
in order to determine what would be ideal. Keep in
mind that excess weight can have health-associated
problems that do not result for quite a while. It
can make arthritis or low back problems worse, cause
diabetes and gall bladder disease. Risk of Type II
diabetes (usually adult onset) rises in women at a
BMI of over 22 even though the normal range for BMI
is 19-25. Deaths from cardiovascular disease in non-smoking
women rises slightly at a BMI of 22-25 but takes a
dramatic jump at a BMI of over 30. Each kilogram (2.2
lbs) of weight loss will reduce systolic blood pressure
(the first number) by .43 mm Hg and diastolic blood
pressure (the second or bottom number) by .33 mm HG
in women who have hypertension.
Certain cancers have also been associated with excess
weight. Cancer of the gall bladder, breast, uterus
and ovaries are more common in obese women and weight
loss seems to significantly reduce these risks. Obesity
is also a risk factor in for osteoarthritis which
is the condition responsible for more than 70% of
hip and knee replacements. In overweight individuals
weight loss of an average of 11 lbs (5 kg) reduced
the risk of developing osteoarthritis by more than
50%.
BMIs of 28-30 have a 2.4 times risk of infertility
and ovulatory disorders compared to women with a BMI
of 20-22. Excess hair growth and acne can also be
associated with increased weight and disappear with
weight loss.
What is the definition of overweight or obesity?
While BMI is not the perfect measurement for assessing
increased body fat, it is the most easily obtained
measurement that has a high correlation with percent
of body fat so most of the standards are set using
BMI. Even though there can be some increased health
risks within the upper limits of the normal range,
various groups such as the World Health Organization,
the American Institute of Nutrition and the International
Obesity task force, among others have given some guidelines.
Weight Category Definitions
Classification BMI Body Mass Index
Underweight less than 18.5
Normal 18.5 - 24.9
Overweight 25.0 - 29.9
Obesity 30.0 - 39.9
Extreme Obesity 40.0 and greater
You may calculate your body mass index in pounds
or kilograms or look up on the table below where your
current BMI puts you. |
